Stimulants - drugs that stimulate the central nervous system. Typically, an individual under the influence of a stimulant may be talkative, appear confident, appear to have lots of energy, have difficulty resting and be 'on the go'. Examples include amphetamine, cocaine powder (and other forms such as 'crack' cocaine), caffeine, ecstacy (although there may also be hallucinatory effects).

Depressants - drugs that have a depressive effect on the central nervous system. Typically, someone under the influence of a depressant drug may appear uncoordinated or unsteady on their feet, may giggle or laugh out of context, may appear preoccupied or lost in their thoughts, their speech may be slurred or the context may not make much sense. Examples include alcohol, benzodiazepines, cannabis, heroin.

Hallucinogens - these drugs have a profound effect on perception. Hallucinations can occur in any of the five senses. The individual may experience feelings of depersonalisation and a loss of connectedness to their environment, thoughts may become disordered and everyday objects may take on sinister form or cause uncontrollable laughter. Examples include lysergic acid dithylamide (LSD), psilocybin mushrooms ('magic' mushrooms) and diemethyltryptamine (DMT).

New Psychoactive Substances - named as so-called 'legal highs' prior to legislation in 2016. They are now illegal to produce, sell or be in possession of in a custodial institution. Different products are designed to produce the kinds of effects referred to in the sections above. However, the greatest risk with these substances is the untested nature of them. It is impossible to produce one of these substances and know with certainty how it will affect users, especially in relation to 'safe' doses of the substance. There are many examples of these chemicals and they may still be available on the internet and through dealers of 'traditional' drugs.